Raymond : The Chazy Formation and its Fauna. 583 



5. A mass more or less siliceous, and more massive ; it contains the Iso- 

 tehis and Illtcniis, twenty feet. 



6. Mineral characters similar to the foregoing ; the fossils are mostly 

 Orthidse, of which individuals of two or three species are very numerous. 



7. Red crinoidal mass, with less earthy matter, and is susceptible to a 

 fine polish ; fifteen feet thick. 



8. Drab-colored, thin-bedded magnesian limestone, suitable for hydraulic 

 lime. 



In southwestern Virginia and in Tennessee the Chazy is stated to occupy 

 the same position and carry the same fossils as at Chazy and Essex. Its 

 thickness there is 130 feet. 



The following fossils are described : 



Oi'thoceras rectianmtlatiis, Atrypa acutirosta, 



0. subarcuaius, Atrypa dubia, 

 Maclurca magna, Orthis costalis, 

 Maclurea sordida, Strophomena insctilpta, 

 S(raparollus labiatiis, Strophomena fasciata, 

 Straparollus angulatus, Stictopora labyrinthica, 

 Scalites angulatus, Stictopora fenestrata , 

 Raphistoma striata, Cobtmnaria alveolata, 

 Raphistoma planistria, Streptoplasma expansa, 

 Raphistoma staminea, Calasies tenuiradiatus, 

 Pleicrotomaria antiqitala, IlUcntis crassicauda, 

 Biicania sulcatina, Ilhcmts arcturus, 

 Bucania rotundata, Isotelus canalis, 

 Atrypa plicifera, Asaphtts obtusus, 

 Atrypa plena, Asaphus niarginalis. 

 Atrypa altilis, 



1855. M.\RCOU, Jules. Resume Explicatif d'une Carte Geologique des Etats-Unis 

 et des Provinces Anglais de T Amerique du Nord, avec un Profil Geologique 

 Allant de la Vallee du Mississippi au.x Cotes du Pacifique, et une Planche de 

 Fossiles. Bulletin of the Geological Society of France, 2d series. Vol. 12, 

 pt. 2, pp. 813-914. 



In the " Silurian moyen,'" Marcou places: first, the Chazy or Isle La 

 Motte limestone ; second, Birdseye limestone ; third. Black River lime- 

 stone ; fourth, Trenton limestone ; fifth, Utica slate ; and sixth, Hudson 

 River group. Among the principal fossils Maclurea magna is listed. 



1858. BiGSBV, Dr. J. J. On the Paleozoic Basin of the State of New York. Part 



1. Quarterly Journal of the Geological Society of London, Vol. XIV, 332, 

 pt. 2, p. 427, pt. 3, Vol. XV, p. 251. 



The thickness of the Chazy or Black River Limestone, including the 

 Birdseye, is given at 130 feet. 



Sixty-three fossils are listed, divided among the groups as follows : 

 Zoophyta 5, Bryozoa 5, Echinodermata 3, Brachiopoda 12, Monomyaria i, 

 Crustacea 6, Gastropoda 14, Cephalopoda 17. This list, however, contains 



